1. Field of the Invention
The present invention relates to a lens barrel and an image pickup apparatus.
2. Description of the Related Art
As a type of lens barrels for image pickup apparatuses such as digital still cameras, a collapsible lens barrel is provided, in which a lens frame for supporting a part of a lens defining an imaging optical system moves in an optical-axis direction of the lens such that the lens protrudes and is retracted from a front surface of a case.
A configuration using a cam ring and a fixed ring is suggested as an example configuration for moving such a lens frame in the optical-axis direction (see Japanese Unexamined Patent Application Publication No. 2007-114528).
In this lens barrel, the cam ring has a lens-frame-movement cam groove formed in an inner or outer peripheral surface, a cam follower protruding outward in a radial direction of the outer peripheral surface, and a gear portion protruding outward in the radial direction of the outer peripheral surface and extending in a circumferential direction.
The fixed ring has a cam-ring-movement cam groove and a gear housing recess for housing the gear portion in an inner peripheral surface. The cam follower engages with the cam-ring-movement cam groove.
The cam ring is inserted into the fixed ring, the cam follower of the cam ring engages with the cam-ring-movement cam groove, then, a drive gear meshes with the gear portion, and the cam ring is rotated. Hence, the cam ring moves between a retracted position and a protruding position via the cam follower and the cam-ring-movement cam groove while the cam ring is rotated inside the fixed ring. The gear portion thus moves inside the gear housing recess with the cam ring while the gear portion meshes with the drive gear.
Meanwhile, in recent years, a compact image pickup apparatus is demanded. Thus, a lens barrel advantageous to reducing the size is desired. It is therefore necessary to reduce the size of the fixed ring.